
©Silberschatz, Korth and Sudarshan6.57Database System Concepts - 5th Edition, Oct 5, 2006
Composite and
Composite and Multivalued
Multivalued Attributes
Attributes
Composite attributes are flattened out by creating a separate attribute for
each component attribute
zExample: given entity set customer with composite attribute name with
component attributes first_name and last_name the schema
corresponding to the entity set has two attributes
name.first_name and name.last_name
A multivalued attribute Mof an entity Eis represented by a separate
schema EM
zSchema EM has attributes corresponding to the primary key of Eand
an attribute corresponding to multivalued attribute M
zExample: Multivalued attribute dependent_names of employee is
represented by a schema:
employee_dependent_names = (employee_id, dname)
zEach value of the multivalued attribute maps to a separate tuple of the
relation on schema EM
For example, an employee entity with primary key 123-45-6789
and dependents Jack and Jane maps to two tuples:
(123-45-6789 , Jack) and (123-45-6789 , Jane)